1. Field of the Invention
The present invention relates to a temperature sensor using a thermistor element.
2. Description of the Related Art
There is a temperature sensor incorporating a thermistor element capable of measuring the temperature of an exhaust gas emitted from an internal combustion engine mounted on a vehicle. Japanese laid open publication NO. 2000-97781 had disclosed such a conventional temperature sensor incorporating a thermistor element whose resistance value is changed according to an ambient temperature change.
Such a temperature sensor is composed of a thermistor element incorporating a pair of electrodes, a sheath pin incorporating a pair of signal lines connected to the electrode pair therein, and a cover located at a front part of the temperature sensor, which covers the thermistor element.
However, in the above conventional temperature sensor, the thermistor element is only connected to a pair of the signal lines in the sheath pin. When the temperature sensor is vibrated, for example, during the running of the vehicle on which the temperature sensor is mounted, the thermistor element is vibrated, and the vibration brings the temperature sensor to a possibility of forcedly contacting the thermistor element with the cover. In particular, when the temperature sensor is placed near the internal combustion engine of the vehicle, severe or large vibration is applied to the temperature sensor, and the vibration increases a possibility of forcedly contacting the temperature sensor with the cover, and severe shock is thereby applied to the thermistor element.
In order to avoid this drawback, another conventional technique, for example, Japanese patent 3296034 has disclosed a temperature sensor in which the inside space in a cover in which a thermistor element is embedded is filled with cement having a superior thermal conductivity in order to forcedly fix the thermistor element to the cover by the cement. In the manufacturing process of producing such a temperature sensor, cement and water are mixed at the beginning, and the cement involving water is poured into the inside space of the cover, and then the thermistor element connected to the signal lines of the sheath pin is inserted into the cover, and the cement involving water is dried in order to evaporate the water component and to support and tightly fix the thermistor element to the cover. However, this conventional technique requires a positioning tool to position and place the thermistor element at an optimum position in the inside of the cover without contacting the thermistor element with the cover. The conventional temperature sensor has a tapered part formed in a part of the cover, and the thermistor element is positioned while contacting a front part of the sheath pin with the taper part of the cover. This conventional positioning manner using the positioning tool satisfies such a requirement to avoid the drawback described above. (In addition, see FIG. 19, FIG. 20, and FIG. 21 as related-art comparison example.)
However, this technique of the conventional positioning manner technique causes another drawback that the front part of the sheath pin seals up the inside of the cover, and it is thereby difficult to drain, namely, to dry water involved in the cement because the water component involved in the cement is hardly drained from the inside of the cover to the outside of the temperature sensor, and the cement is not dried easily.